Alanine transaminase (ALT), also known as glutamate-pyruvate transaminase (GPT, SGPT), and aspartate transaminase (AST), also known as glutamate-oxaloacetate transaminase (GOT, SGOT), have clinical significance in the diagnosis of disease. Abnormal levels of both transaminases are seen in patients with hepatic disease, myocardial and skeletal muscle necrosis and other diseases.
Methods and multilayer dry elements for assaying both transaminases are known. U.S. Pat. No. 4,897,347 discloses a method and element based on the following chemical reactions: ##STR1##
U.S. Pat. No. 4,897,347 requires that the pyruvate oxidase be present in the uppermost porous layer or in a layer adjacent to the uppermost layer. Reference examples 1 and 2 are presented therein. The elements of these examples involve a layer comprising titanium dioxide layer between the uppermost layer and the layer containing the pyruvate oxidase. These examples show such elements are unsatisfactory in that the range of concentrations of transaminase determinable by the elements is narrow with maximum concentration of less than 200 U/l. See FIG. 10 thereof.
The problem is that incorporation of enzymes into spreading layers made from dispersed inorganic compounds or polymeric beads in a manner in which enzymatic activity is retained is difficult and often requires a subsequent coating step to add the enzyme to a preformed spreading layer. Moreover spreading layers generally require a subbing layer between them and underlying reagent layers for adherence. Also pyruvate oxidase is expensive.